System and method for hemming vehicle sheet metal

ABSTRACT

A vehicle sheet metal hemming system ( 20 ) and method for hemming vehicle sheet metal outer and inner members ( 24  and  26 ) to each other is performed by prehemming and final hemming operations at a single station in cooperation with robot apparatus ( 42 ). A drive mechanism ( 98 ) has a rotary actuator ( 100 ) that moves a tool table ( 78 ) vertically to move tool heads ( 80 ) between outer idle positions and inner use positions as well as moving prehem tools ( 82 ) and final hem tools ( 84 ) of the tool heads so as to perform both the prehemming and the final hemming operations.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a system and method for hemming vehicle sheetmetal outer and inner members to each other.

2. Background Art

Vehicle sheet metal components conventionally include outer and innermembers having peripheries that are secured to each other by a hemmingoperation. The outer member of such components defines the vehicle outersurface while the inner member functions to provide structural supportand/or attachment of the component to the vehicle or attachment of othervehicle components. Conventionally the hemming is performed by formingthe periphery of the outer member around the inside of the periphery ofthe inner member. The hemming operation is conventionally performed by alinear actuator such as a gas or hydraulic cylinder that provides theforming of the outer member around the inner member and then isreciprocated back to the initial start position in preparation for thenext cycle.

Since the forming of the periphery of the outer member around theperiphery of the inner member defines a relatively narrow U-shaped finalconfiguration, often the hemming is performed in two steps at twodifferent stations. More specifically, the outer member to be formed isinitially provided as a stamping having a perpendicular flange at itsperiphery. The first hemming step is performed at a “prehem” station tobend the outer member flange approximately 45 degrees around theperiphery of the inner member. The partially hemmed assembly is thenmoved to a final hemming station where the flange is further formedagainst the periphery of the inner member to complete the hemmingoperation. The hemmed assembly of the outer and inner members is thendelivered from the final hemming station for any other furtherprocessing, assembly or other further processing required.

Prior art hemming is disclosed by the following United States Patentswhich are assigned to the assignee of the present invention. These priorart United States Patents include: U.S. Pat. No. 4,706,489 Dacey, Jr.;U.S. Pat. No. 4,827,595 Dacey, Jr.; U.S. Pat. No. 4,928,388 Dacey, Jr.;and U.S. Pat. No. 5,083,355 Dacey, Jr.

SUMMARY OF THE INVENTION

One object of the present invention is to provide an improved vehiclesheet metal hemming system.

In carrying out the above object, the vehicle sheet metal hemming systemaccording to the invention includes a part supply for providing vehiclesheet metal outer and inner members. A hemming machine of the systemcyclically hems a periphery of an outer member to a periphery of anassociated inner member. Robot apparatus of the system cyclicallytransfers an outer member and an associated inner member from the partsupply to the hemming machine. A base of the hemming machine has astationary part mount that receives outer and inner members to be hemmedto each other. A tool table of the machine is supported for verticalmovement on the base and has a plurality of tool heads mounted thereonfor movement relative to the table inwardly and outwardly with respectto the part mount on which the outer and inner members are mounted. Eachtool head includes a prehem tool mounted thereon for movement relativethereto between: an inner use position for performing prehemming of theouter periphery of the outer member with respect to the periphery of theinner member, and an outer idle position spaced outwardly from the inneruse position. Each tool head also includes a final hem tool forcompleting the hemming of the periphery of the outer member to theperiphery of the inner member. A rotary actuator of the hemming machinehas an output that rotates 360 degrees to move the tool table verticallyon the base from an upper start position downwardly through a hemmingstroke to a lower position and then upwardly back to the upper startposition in preparation for another cycle. A first set of cam mechanismsof the hemming machine moves the tool heads from outer idle positions onthe tool table to inner use positions during the initial downwardmovement of the tool table under the impetus of the rotary actuator suchthat continued downward movement of the tool table then moves theprehemmed tool of each tool head to perform the prehem of the peripheryof the outer member to the periphery of the inner member. A second setof cam mechanisms of the hemming machine moves the prehem tools of thetool heads from their use positions to their outer idle positions uponfarther downward movement of the tool table to permit the final hemtools to complete the hemming of the periphery of the outer member tothe periphery of the inner member under the impetus of the rotaryactuator as the tool table reaches the lower position.

The construction and operation of the hemming system and the hemmingmachine provides hemming of the entire periphery of the outer member tothe inner member at a single station and has particular utility in themanufacturing of vehicle fuel doors.

The rotary actuator of the hemming machine includes an electric motordrive, a clutch, and a gear reducer that drive the rotary output formoving the tool table between its upper start and lower positions.

The robot apparatus of the hemming system includes: a first robot forcyclically transferring outer members from the part supply to the partmount of the hemming machine, a second robot for cyclically transferringan inner member from the part supply to the part mount of the hemmingmachine after prior transfer of the associated outer member thereto, andthe second robot subsequently delivering the hemmed outer and innermembers from the hemming machine.

Four vertical guides of the hemming machine support the tool table forits vertical movement between the upper start position and the lowerposition. Two of the guides have upper connections to the tool table andlower connections to the output of the rotary actuator to providevertical movement of the tool table under the operation of the rotaryactuator. These four vertical guides are spaced horizontally around thestationary part mount of the base at approximately 90 degrees from eachother. The two vertical guides having the upper and lower connectionsare spaced from each other 180 degrees with the two other verticalguides therebetween. The other two vertical guides have locators thatcooperate with the robot apparatus to locate the inner member withrespect to the part mount during the hemming operation. Morespecifically, the locators are positioned at upper ends of the other twovertical guides and locate an end effector of the second robot tothereby position the inner member during the hemming.

The output of the rotary actuator includes a connection bar havingopposite ends that include lower connections to the two vertical guidesthat also have the upper connections to the tool table, and theconnection bar has an intermediate portion extending between itsopposite ends. The output of the rotary actuator of the hemming machinealso includes a rotatively driven eccentric link and a connection linkhaving one end including a pivotal connection to the eccentric link andhaving another end including a pivotal connection to the intermediateportion of the connection bar between its lower connections to the twovertical guides that also have the upper connections to the tool table.

The tool table is disclosed as including four tool heads spaced at 90degrees from each other. The two vertical guides that have the upper andlower connections are spaced from each other 180 degrees with the othertwo vertical guides therebetween, and the tool table includes four toolheads spaced at 90 degrees from each other between the four verticalguides in an alternating relationship.

The construction of the tool table and its tool heads permits the entireperiphery of the outer member to be formed for hemming to the peripheryof the inner member at a single station with both prehem and final hemforming operations.

The first set of cam mechanisms of the hemming machines includes fourslotted cam members mounted on the base and respectively associated withthe four tool heads. Four roller cam followers of the first set of cammechanisms are respectively mounted by the four tool heads andrespectively moved by the four slotted cam members on the base to movethe tool heads between the outer idle positions and the inner usepositions during the vertical movement of the tool table under theimpetus of the rotary actuator.

The second set of cam mechanisms includes four roller cams mounted onthe stationary part mount of the base and also includes four plate camfollowers respectively mounted by the prehem tools of the four toolheads and respectively moved by the four roller cams on the stationarypart mount of the base to move the prehem tools relative to the toolheads from the inner use positions to the outer idle positions aftercontinued downward movement of the tool head subsequent to completion ofthe prehemming. The four roller cams of the second set of cam mechanismseach include two cam rollers spaced from each other such that theassociated tool head moves therebetween, the second set of cammechanisms and the four plate cam followers of the second set of cammechanisms each includes two cam plates that are respectively moved bythe associated two cam rollers on the stationary part mount of the baseto provide the movement of the prehem tools relative to the tool headsfrom the inner use positions to the outer idle positions upon continueddownward movement of the tool table subsequent to completion of theprehemming.

Another object of the present invention is to provide an improved methodfor hemming vehicle sheet metal.

In carrying out the above object, the vehicle sheet metal hemming methodis performed by operating robot apparatus to cyclically transfer avehicle sheet metal outer member and an associated vehicle sheet metalinner member from a part supply to a hemming machine that includes abase having a stationary part mount that receives outer and innermembers to be hemmed to each other and that also includes a tool tablesupported for vertical movement on the base and having a plurality oftool heads mounted thereon for movement relative to the table inwardlyand outwardly with respect to the part mount on which the outer andinner members are mounted. Operation of a rotary actuator having anoutput that rotates 360 degrees moves the tool table vertically on thebase from an upper start position downwardly through a hemming stroke toa lower position and then upwardly back to the upper start position inpreparation for another cycle. During the initial downward movement ofthe tool table under the impetus of the rotary actuator, a first set ofcam mechanisms moves the tool heads on the tool table from outer idlepositions to inner use positions such that continued downward movementof the tool table then moves a prehem tool of each tool head to performa prehem of the periphery of the outer member to the periphery of theinner member. Upon further downward movement of the tool table, a secondset of cam mechanisms subsequently moves the prehem tools of the toolheads from inner use positions to outer idle positions to permit finalhem tools of the tool heads to complete the hemming of the periphery ofthe outer member to the periphery of the inner member under the impetusof the rotary actuator as the tool table reaches the lower position.

The hemming method has particular utility in making vehicle sheet metalfuel doors.

The objects, features and advantages of the present invention arereadily apparent from the following detailed description of thepreferred embodiment for practicing the invention when taken inconnection with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a plan schematic view of a vehicle sheet metal hemming systemthat is constructed in accordance with the invention and provides thevehicle sheet metal hemming method of the invention.

FIG. 2 is an exploded perspective view illustrating a lower vehiclesheet metal outer member and an upper vehicle sheet metal inner memberto be hemmed to each other by the system and method of the invention.

FIG. 3 is a perspective view showing the vehicle sheet member outer andinner members after their peripheries have been hemmed to each other asan assembly.

FIG. 4 is a perspective view of the hemming machine of the hemmingsystem.

FIG. 5 is an elevational view of the hemming machine showing a tooltable thereof in an upper start position which corresponds tocommencement of a hemming cycle.

FIG. 6 is an enlarged view of a portion of FIG. 1 but with its tooltable removed to illustrate the construction of a base, part mount, andfirst and second cam mechanisms of the hemming machine.

FIG. 7 is a view similar to FIG. 5 but showing the hemming machine withits tool table in a lower position which corresponds to completion ofthe hemming cycle.

FIG. 8 is a view similar to FIG. 6 showing the hemming machine with thetool table partially removed to facilitate illustration of the machinebase, part mount, and first and second cam mechanisms.

FIG. 9 is a top perspective view of the hemming machine shown at thecommencement of the hemming cycle which corresponds to the illustrationsin FIGS. 5 and 6.

FIG. 10 is a top perspective view similar to FIG. 9 but shown at thecompletion of the hemming cycle which corresponds to the illustrationsin FIGS. 7 and 8.

FIG. 11 is an exploded perspective view showing one of the tool headsand its prehem tool and final hem tool.

FIG. 12 is a perspective view showing a part mount of the machine baseon which the outer and inner members are mounted during the hemmingcycle.

FIG. 13 is a view that illustrates the vehicle sheet metal outer andinner members just before downward movement of the tool heads hascommenced the prehem operation.

FIG. 14 is a view similar to FIG. 13 but after completion of the prehemoperation.

FIG. 15 is a view similar to FIG. 14 after outward movement of theprehem tool and continued downward movement of the tool head has movedthe final hem tool to preform the final hemming that completes thehemming operation.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

With reference to FIG. 1, a schematically indicated vehicle sheet metalhemming system is indicated generally by 20 and is constructed inaccordance with the invention as well as performing a vehicle sheetmetal hemming method according to the invention as is hereinafter morefully described. The hemming system 20 and the hemming method of theinvention will be described in an integrated manner to facilitate anunderstanding of all aspects of the invention.

The hemming system 20 includes a part supply collectively indicated by22 for providing vehicle sheet metal outer and inner members 24 and 26as shown in FIG. 2. As illustrated in FIG. 1, the outer members 24 areprovided by an outer member subsupply 28 and the inner members 26 areprovided by an inner member subsupply 30.

With continuing reference to FIG. 1, a hemming machine 32 of the hemmingsystem 20 cyclically hems a periphery 34 of the outer member 24 to aperiphery 36 of an associated inner member 26 as shown in FIG. 3 toprovide an assembled vehicle sheet metal component 38 as shown in FIG.3. As is hereinafter more fully described, the specific assembledvehicle sheet metal component 38 illustrated is a fuel door whose innermember 36 provides attachment to an associated hinge for moving the fueldoor between open and closed positions through the assistance of a thumbhold 40 in the outer member 34 which provides the continuation of thevehicle outer surface around the associated fuel door opening. The innermember 26, as shown in FIGS. 2 and 3, includes two or more deformationsat its periphery 36 for contacting the outer member 24 to assist inpreventing movement of the inner member with respect to the outer memberafter the hemming. It should also be appreciated that not all fuel doorshave thumb holds, since some fuel doors have spring assisted openingafter release by an internal actuator within the vehicle occupantcompartment. In such cases the outer member will provide continuity ofthe outer vehicle surface around the fuel door opening.

The hemming machine 32 has particular utility in providing the hemmingof the entire periphery 34 of the outer member 24 to the periphery 36 ofthe inner member 26 during a single hemming operation which consists ofan initial prehemming step and a subsequent final hemming step performedat a single location so as to facilitate the assembling of the outer andinner members to each other.

With reference back to FIG. 1, robot apparatus collectively indicated by42 cyclically transfers an outer member 24 and an associated innermember 26 from the part supply 22 to the hemming machine 32. Morespecifically, the robot apparatus includes a first robot 44 having anarm 46 that supports an end effector 48 for cyclically moving the outermembers from the subsupply 28 to the hemming machine 32 as the robot arm46 is moved between its solid and phantom line positions. After suchtransfer, the robot arm 46 is then moved back to its solid line positionto start the next cycle. The robot apparatus 42 also includes a secondrobot 50 having an arm 52 which supports an end effector 54 thatcyclically moves the inner members from the second subsupply 30 to thehemming machine after the first robot 44 has moved the associated outermember to the hemming machine. The second robot 50 maintains its arm 52at the hemming machine positioning the inner and outer members withrespect to each other and after the hemming operation moves the hemmedsheet metal assembly 38 to a delivery station 56 which may be a bin,conveyor, etc.

As illustrated in FIGS. 4-8, the hemming machine includes a base that isgenerally indicated by 58 and has lower feet 60 mounted on the factoryfloor 62, a lower base member 64, vertical columns 66 that extendupwardly from the lower base member, an upper base member 68 supportedby the column 66 above the lower base member in a spaced relationship,and a part mount 70 best illustrated in FIG. 12 and mounted on the upperbase member 68 to receive the sheet metal outer and inner members to behemmed to each other as previously described in connection with therobot apparatus. More specifically with reference to FIG. 12, the partmount 70 has an upper surface 72 including a peripheral depression 74where the thumb hold of the outer member is positioned. In addition,locators 76 project upwardly from the upper surface 72 to provideperipheral positioning of the outer member which then receives the innermember as previously described. The part mount 70 may also have anupwardly projecting peripheral die ring, instead of the locators 76, forpositioning the outer member 24 during the hemming. The inner memberpositioning is also achieved in cooperation with the end effector 54 ofthe second robot 50 shown in FIG. 1 as previously described and, afterthe hemming operation, the sheet metal assembly 38 is moved upwardlyfrom the part mount 70 and moved to the delivery station 56 as the firstrobot 44 moves the next outer member from the first substation 28 to thepart mount as previously described in preparation for the next cycle.The second robot 50 then is operated so that its end effector 54 movesanother inner member from the second subsupply 30 to the part mount forthe next hemming operation.

The hemming machine 32 also includes a tool table 78 supported forvertical movement on the upper base member 68 of base 58 from the upperstart portion of FIG. 5 to the lower position of FIG. 7 as ishereinafter more fully described. The tool table 78 includes a pluralityof tool heads 80, four as shown, mounted thereon for movement relativeto the table inwardly and outwardly with respect to the part mount 70 onwhich the outer and inner members are mounted for the hemming operation.Each tool head 80 as shown in FIG. 11 includes a prehem tool 82 and afinal hem tool 84. Bolts 86 extend through holes in the final hem tool84 and into holes 88 in the tool head 80 to fixedly mount the final hemtool thereon. The prehem tool 82 has a mounting portion 90 that isreceived within a downwardly opening slideway 92 in the final hem tool84 to support the prehem tool for movement between an inner use positionas illustrated in FIGS. 13 and 14 and an outer idle position asillustrated in FIG. 15. The prehem tool 82 has a tool surface 94 that iscurved for approximately 90 degrees about the central axis of the partmount and has an inclination of approximately 45 degrees with respect tothe horizontal. During downward movement of the tool heads as ishereinafter described, the prehem tool 82 is moved from the position ofFIG. 13 to the position of FIG. 14 in its inner use position to preformprehemming of the outer periphery 34 of the outer member 24 with respectto the periphery 36 of the inner member 26. Thereafter as is hereinaftermore fully described, outward movement of the prehem tool 82 to the idleposition of FIG. 15 and continued downward movement of the tool headmoves a tool surface 96 of the final hem tool 84 into engagement withthe outer member periphery 36 and downwardly into the final positionshown to complete the hemming operation. This tool surface 96 of thefinal hem tool 84 extends with a curved shape around the central axis ofthe part mount for approximately 90 degrees with a horizontalorientation to provide the final hemming step.

As shown in FIGS. 4, 5 and 7, a drive mechanism 98 of the hemmingmachine includes a rotary actuator 100 having an output 102 that movesthe tool table 78 vertically on the upper base member 68 of base 58 froman upper start position as shown in FIG. 5 through a hemming stroke to alower position as shown in FIG. 7 and then upwardly back to the upperstart position in preparation for another cycle. More specifically, therotary output 102 rotates in the direction of arrow 104 in FIG. 5 for180 degrees to move the tool table through the hemming stroke as ishereinafter more fully described until reaching the lower position ofFIG. 7 which corresponds to the final hemming illustrated in FIG. 15.Thereafter, continued rotation of the rotary output 102 in the directionof arrow 106 shown in FIG. 7 for 180 degrees moves the tool table backupwardly to the position of FIG. 5 in preparation for the next cycle. Inthis upper position, the rotary operation dwells for a predeterminedtime to permit unloading of the hemmed sheet metal assembly and loadingof the next outer and inner members to be hemmed to each other.

As best illustrated in FIGS. 9 and 10, the hemming machine 32 includes afirst set of cam mechanisms 108 for moving the tool heads 80 from outeridle positions as shown in FIG. 9 to inner use positions as shown inFIG. 10 during the initial downward movement of the tool table 78 underthe impetus of the rotary actuator 100 of the drive mechanism. Thisinitial movement corresponds with the movement of the FIG. 6 right cammechanism 108 from its solid line indicated position to its phantom lineindicated position and positions the tool heads for the prehemmingoperation during the downward movement from the position of FIG. 13 tothe position of FIG. 14, as previously described, and for the subsequentfinal hemming during the downward movement to the position shown in FIG.15. After completion of the hemming operation, subsequent upwardmovement of the tool table 78 back to its upper position causes the cammechanisms 108 to move the tool heads 80 back to their outer positionsas shown in FIGS. 5 and 6. Linear bearings 110 best shown in FIGS. 6, 8and 11 mount the tool heads 84 for their inward and outward movementunder the operation of the cam mechanisms 108 whose construction ishereinafter more fully described.

As illustrated in FIGS. 6, 8, 11 and 12, a second set of cam mechanisms112 move the prehem tools 82 of the tool heads 80 from their inner usepositions illustrated in FIGS. 6, 13 and 14 to their outer idlepositions illustrated in FIGS. 8 and 15 upon farther downward movementof the tool table to permit the final hem tools to complete the hemmingof the periphery 34 of the outer members to the periphery 36 of theinner members 24 as previously described in connection with FIG. 15.This movement is under the impetus of the rotary actuator 100 of drivemechanism 98 as the tool table 68 reaches the lower position illustratedin FIG. 8. The construction of the second set of cam mechanisms 112 aswell as the first set of cam mechanisms 108 is hereinafter more fullydescribed in detail.

As illustrated in FIG. 4, the rotary actuator 100 of drive mechanism 98includes an electric motor drive 114, a clutch 116, and a gear reducer118 that rotatively drive the rotary output 102 for moving the tooltable between its upper start position of FIG. 5 and its lower positionof FIG. 7. The clutch 116 disengages to prevent any machine damage incase of malfunction while the gear reducer 118 reduces the speed ofrotation of the electric motor drive 114.

As shown by combined reference to FIGS. 4, 5, 9 and 10, the hemmingmachine includes two vertical guides 120 spaced diametrically oppositeeach other from the central axis of the part mount and two othervertical guides 122 spaced diametrically opposite each other withrespect to the part mount, with the vertical guides 120 and 122alternating with each other and being spaced circumferentially about thecentral axis of the part mount at 90 degrees from each other. The twovertical guides 120 are linear bearings that provide a guiding functionof the tool table 78 on the upper base member 68 of the base 58. Thesetwo vertical guides 120 have upper locators 123 that locate the endeffector 54 of the second robot 50 to locate the inner member 26 withrespect to the part mount 70 during the hemming operation. The other twovertical guides 122 in addition to providing such vertical guiding alsoprovide connection of the tool table 78 to the rotary actuator 100 ofthe drive mechanism 98 in order to provide the actuation of the tooltable vertical movement.

More specifically, the two vertical guides 122 have upper connections124 to the tool table 78 as shown in FIGS. 9 and 10 and have lowerconnections 126 to the rotary actuator 100 as shown in FIGS. 5 and 7.The four vertical guides 120 and 122 are thus spaced horizontally aroundthe stationary mount 70 on the upper base member 68 of base 58 atapproximately 90 degrees from each other with the two vertical guides122 having the upper and lower connections 124 and 126 being spaced fromeach other 180 degrees with the two vertical guides 122 therebetween.The output 102 of the rotary actuator 100 includes a connection bar 128shown in FIGS. 5 and 7 as having opposite ends 130 that include thelower connections 126 to the vertical guides 122 that also have theupper connections 124 to the tool table 78. This connection bar 128 alsohas an intermediate portion 132 extending between its opposite ends. Theoutput 102 of the rotary actuator 100 includes a rotatively driveneccentric link 134 and a connection link 136 having one end 138including a pivotal connection 140 to the eccentric link and havinganother end 142 including a pivotal connection 144 to the intermediateportion 132 of the connection bar 128 between its lower connections 126to the two vertical guides 122 that also have the upper connections tothe tool table.

As illustrated in FIGS. 9 and 10, the four tool heads 80 of the tooltable 78 are spaced at 90 degrees from each other between the fourvertical guides 120 and 122 in an alternating relationship. Four toolhead slideways 146 are respectively associated with the tool heads 80and each has lower mounts 148 fixedly secured to the tool table 78 aswell as each having an upper support 150 that extends between the lowermounts and is slidably engaged by the final hem tool 84 of theassociated tool head to prevent upward movement thereof during both theprehemming and final hemming operations previously described inconnection with FIGS. 12-15.

As illustrated in FIGS. 4-10, the first set of cam mechanisms 108includes four slotted cam members 152 mounted on the upper base member68 of the base 58 and respectively associated with the four tool heads80. Each of the cam members 152 has a slot 154 having an outwardlyinclined upper end and a vertical lower end best shown in FIGS. 6 and 8.The first set of cam mechanisms also includes four roller cam followers156 respectively mounted by the four tool heads 80 and received by theslots 154 of the four cam members 152 on the base to move the tool headsbetween the outer idle positions and the inner use positions during thevertical movement of the tool table under the impetus of the rotaryactuator 100 previously described.

The second set of cam mechanisms 112 as shown in FIG. 12 includes fourpairs of roller cams 158 that are mounted on the stationary part mount70 on the upper base member 68 of the base 58 and respectivelyassociated with the four tool heads. The roller cams 158 of each pairare spaced from each other such that the four tool heads movetherebetween during the inward and outward movement under the operationof the first set of cams as described above. The second set of cammechanisms 112 also includes four pairs of plate cam followers 160 witheach pair being mounted on one of the prehemmed tools 82, as shown inFIG. 11, on opposite sides of its tool surface 94. Each prehem tool 82also includes a threaded adjuster that is engaged with a gas spring 164of the associated tool head 80 to bias the prehem tool to its inner useposition. After the rotary actuator 100 has moved the tool table 78downwardly sufficiently so that the prehemming has been performed asillustrated in FIG. 14, the plate cam followers 160 engage the rollercams 158 and move the prehem tools 82 outwardly against the bias of gassprings 164 as illustrated in FIG. 11 to the outer idle position shownin FIG. 15 so that the final hem tools 84 can complete the hemmingoperation as previously described.

The sheet metal hemming system 20 of the invention thus providesefficient loading of the inner and outer members by the robot apparatusfor both the prehem and final hemming operations as well providingdelivery of the sheet metal assembly after the hemming from the singlestation where both the prehem and final hemming operations are performedby rotary actuation of the drive mechanism.

While the best mode for practicing the invention has been described indetail, those familiar with the art to which this invention relates willrecognize various alternative designs and embodiments for practicing theinvention as defined by the following claims.

1. A vehicle sheet metal hemming system comprising: a part supply forproviding vehicle sheet metal outer and inner members; a hemming machinefor cyclically hemming a periphery of an outer member to a periphery ofan associated inner member; robot apparatus for cyclically transferringan outer member and an associated inner member from the part supply tothe hemming machine; the hemming machine including a base having astationary part mount that receives outer and inner members to be hemmedto each other; a tool table supported for vertical movement on the baseand having a plurality of tool heads mounted thereon for movementrelative to the table inwardly and outwardly with respect to the partmount on which the outer and inner members are mounted; each tool headincluding a prehem tool mounted thereon for movement relative theretobetween: an inner use position for preforming prehemming of theperiphery of the outer member with respect to the periphery of the innermember, and an outer idle position spaced outwardly from the inner useposition; each tool head also including a final hem tool for completingthe hemming of the periphery of the outer member to the periphery of theinner member; a drive mechanism including a rotary actuator having anoutput that rotates 360 degrees to move the tool table vertically on thebase from an upper start position downwardly through a hemming stroke toa lower position and then upwardly back to the upper start position inpreparation for another cycle; a first set of cam mechanisms for movingthe tool heads from outer idle positions on the tool table to inner usepositions during the initial downward movement of the tool table underthe impetus of the rotary actuator such that continued downward movementof the tool table then moves the prehem tool of each tool head toperform the prehem of the periphery of the outer member to the peripheryof the inner member; and a second set of cam mechanisms for moving theprehem tools of the tool heads from their inner use positions to theirouter idle positions upon farther downward movement of the tool table topermit the final hem tools to complete the hemming of the periphery ofthe outer member to the periphery of the inner member under the impetusof the rotary actuator as the tool table reaches the lower position. 2.A vehicle sheet metal hemming system as is claim 1 wherein the rotaryactuator of the drive mechanism includes an electric motor drive, aclutch, and a gear reducer that drive the rotary output for moving thetool table between its upper start and lower positions.
 3. A vehiclesheet metal hemming system as is claim 1 wherein the robot apparatusincludes: a first robot for cyclically transferring outer members fromthe part supply to the part mount of the hemming machine, a second robotfor cyclically transferring an inner member from the part supply to thepart mount of the hemming machine after prior transfer of the associatedouter member thereto, and the second robot subsequently delivering thehemmed outer and inner members from the hemming machine.
 4. A vehiclesheet metal hemming system as in claim 3 further including locators thatcooperate with the second robot to locate the inner member with respectto the part mount during the hemming.
 5. A vehicle sheet metal hemmingsystem as is claim 1 wherein the hemming machine includes four verticalguides that support the tool table for its vertical movement between theupper start position and the lower position, and two of the guideshaving upper connections to the tool table and lower connections to theoutput of the rotary actuator to provide vertical movement of the tooltable under the operation of the rotary actuator.
 6. A vehicle sheetmetal hemming system as is claim 5 wherein the four vertical guides arespaced horizontally around the stationary part mount of the base atapproximately 90 degrees from each other, the two vertical guides havingthe upper and lower connections being spaced from each other 180 degreeswith the other two vertical guides therebetween, the output of therotary actuator including a connection bar having opposite ends thatinclude the lower connections to the two vertical guides that also havethe upper connections to the tool table, and the connection bar havingan intermediate portion extending between its opposite ends.
 7. Avehicle sheet metal hemming system as in claim 6 wherein the two othervertical guides have upper ends including locators that cooperate withthe robot apparatus to locate the inner member with respect to the partmount during the hemming operation.
 8. A vehicle sheet metal hemmingsystem as is claim 6 wherein the output of the rotary actuator alsoincludes a rotatively driven eccentric link and a connection link havingone end including a pivotal connection to the eccentric link and havinganother end including a pivotal connection to the intermediate portionof the connection bar between its lower connections to the two verticalguides that also have the upper connections to the tool table.
 9. Avehicle sheet metal hemming system as is claim 6 wherein the output ofthe rotary actuator also includes a rotatively driven eccentric link anda connection link having one end including a pivotal connection to theeccentric link and having another end including a pivotal connection tothe intermediate portion of the connection bar between its lowerconnections to the two vertical guides that also have upper connectionsto the tool table, and the rotary actuator including an electric motordrive, a clutch and a gear reducer that drive the eccentric link to movethe tool table between its upper start and lower positions.
 10. Avehicle sheet metal hemming system as is claim 5 wherein the fourvertical guides are spaced horizontally around the stationary part mountof the base at approximately 90 degrees from each other, the twovertical guides having the upper and lower connections being spaced fromeach other 180 degrees with the other two vertical guides therebetween,and the tool table including four tool heads spaced at 90 degrees fromeach other between the four vertical guides in and alternatingrelationship.
 11. A vehicle sheet metal hemming system as is claim 10wherein the first set of cam mechanisms includes: four slotted cammembers mounted on the base and respectively associated with the fourtool heads, and four roller cam followers respectively mounted by thefour tool heads and respectively moved by the four slotted cam memberson the base to move the tool heads between the outer idle positions andthe inner use positions during the vertical movement of the tool tableunder the impetus of the rotary actuator.
 12. A vehicle sheet metalhemming system as is claim 10 wherein the second set of cam mechanismsincludes: four roller cams mounted on the stationary part mount of thebase, and four plate cam followers respectively mounted by the prehemtools of the four tool heads and respectively moved by the four rollercams on the stationary part mount of the base to move the prehem toolsrelative to the tool heads from the inner use positions to the outeridle positions after continued downward movement of the tool headsubsequent to completion of the prehemming.
 13. A vehicle sheet metalhemming system as is claim 12 wherein the four roller cams of the secondset of cam mechanisms each includes two cam rollers spaced from eachother such that the associated tool head moves therebetween, and thefour plate cam followers of the second set of cam mechanisms eachincluding two cam plates that are respectively moved by the associatetwo cam rollers on the stationary part mount of the base to provide themovement of the prehem tools relative to the tool heads from the inneruse positions to the outer idle positions upon continued downwardmovement of the tool table subsequent to completion of the prehemming.14. A vehicle sheet metal hemming system as is claim 10 wherein thefirst set of cam mechanisms includes: four slotted cam members mountedon the base and respectively associated with the four tool heads, andfour roller cam followers respectively mounted by the four tool headsand respectively moved by the four slotted cam members on the base tomove the tool heads between the outer idle positions and the inner usepositions during the vertical movement of the tool table under theimpetus of the rotary actuator; and wherein the second set of cammechanisms includes: four roller cams mounted on the stationary partmount of the base, and four plate cam followers respectively mounted bythe prehem tools of the four tool heads and respectively moved by thefour roller cams on stationary part mount of the base to move the prehemtools relative to the tool heads from the inner use positions to theouter idle positions after continued downward movement of the tool tablesubsequent to completing the prehemming.
 15. A vehicle fuel door sheetmetal hemming system comprising: a part supply for providing vehiclesheet metal fuel door outer and inner members; a hemming machine forcyclically hemming a periphery of a fuel door outer member to aperiphery of an associated fuel door inner member; robot apparatus forcyclically transferring a fuel door outer member and an associated fueldoor inner member from the part supply to the hemming machine; thehemming machine including a base having a stationary part mount thatreceives fuel door outer and inner members to be hemmed to each other; atool table supported for vertical movement on the base and having aplurality of tool heads mounted thereon for movement relative to thetable inwardly and outwardly with respect to the part mount on which thefuel door outer and inner members are mounted; each tool head includinga prehem tool mounted thereon for movement relative thereto between: aninner use position for preforming prehemming of the periphery of thefuel door outer member with respect to the periphery of the fuel doorinner member, and an outer idle position spaced outwardly from the inneruse position; each tool head also including a final hem tool forcompleting the hemming of the periphery of the fuel door outer member tothe periphery of the fuel door inner member; a drive mechanism includinga rotary actuator having an output that rotates 360 degrees to move thetool table vertically on the base from an upper start positiondownwardly through a hemming stroke to a lower position and thenupwardly back to the upper start position in preparation for anothercycle; a first set of cam mechanisms for moving the tool heads fromouter idle positions on the tool table to inner use positions during theinitial downward movement of the tool table under the impetus of therotary actuator such that continued downward movement of the tool tablethen moves the prehem tool of each tool head to perform the prehem ofthe periphery of the fuel door outer member to the periphery of the fueldoor inner member; and a second set of cam mechanisms for moving theprehem tools of the tool heads from their inner use positions to theirouter idle positions upon farther downward movement of the tool table topermit the final hem tools to complete the hemming of the periphery ofthe fuel door outer member to the periphery of the fuel door innermember under the impetus of the rotary actuator as the tool tablereaches the lower position.
 16. A vehicle sheet metal hemming systemcomprising: a part supply for providing vehicle sheet metal outer andinner members; a hemming machine for cyclically hemming a periphery ofan outer member to a periphery of an associated inner member, and thehemming machine including a base having a stationary part mount thatreceives outer and inner members to be hemmed to each other; robotapparatus including: a first robot for cyclically transferring outermembers from the part supply to the part mount of the hemming machine, asecond robot for cyclically transferring an inner member from the partsupply to the part mount of the hemming machine after prior transfer ofthe associated outer member thereto, and the second robot subsequentlydelivering the hemmed outer and inner members from the hemming machine;the hemming machine including a tool table supported for verticalmovement on the base and having a plurality of tool heads mountedthereon for movement relative to the table inwardly and outwardly withrespect to the part mount on which the outer and inner members aremounted; each tool head including a prehem tool mounted thereon formovement relative thereto between: an inner use position for preformingprehemming of the periphery of the outer member with respect to theperiphery of the inner member, and an outer idle position spacedoutwardly from the inner use position; each tool head also including afinal hem tools for completing the hemming of the periphery of the outermember to the periphery of the inner member; a drive mechanism includinga rotary actuator having an output and also including an electric motor,a clutch and a gear reducer that drive the rotary output 360 degrees tomove the tool table vertically on the base from an upper start positiondownwardly through a hemming stroke to a lower position and thenupwardly back to the upper start position in preparation for anothercycle; a first set of cam mechanisms for moving the tool heads fromouter idle positions on the tool table to inner use positions during theinitial downward movement of the tool table under the impetus of therotary actuator such that continued downward movement of the tool tablethen moves the prehem tool of each tool head to perform the prehem ofthe periphery of the outer member to the periphery of the inner member;and a second set of cam mechanisms for moving the prehem tools of thetool heads from their inner use positions to their outer idle positionsupon farther downward movement of the tool table to permit the final hemtools to complete the hemming of the periphery of the outer member tothe periphery of the inner member under the impetus of the rotaryactuator as the tool table reaches the lower position.
 17. A vehiclesheet metal hemming system comprising: a part supply for providingvehicle sheet metal outer and inner members; a hemming machine forcyclically hemming a periphery of an outer member to a periphery of anassociated inner member, and the hemming machine including a base havinga stationary part mount that receives outer and inner members to behemmed to each other; robot apparatus including: a first robot forcyclically transferring outer members from the part supply to the partmount of the hemming machine, and a second robot for cyclicallytransferring an inner member from the part supply to the part mount ofthe hemming machine after prior transfer of the associated outer memberthereto, and the second robot subsequently delivering the hemmed outerand inner members from the hemming machine; the hemming machineincluding a tool table having a plurality of tool heads mounted thereonfor movement relative to the table inwardly and outwardly with respectto the part mount on which the outer and inner members are mounted; fourvertical guides that support the tool table for vertical movementbetween an upper start position and a lower position, and two of thevertical guides having upper connections to the tool table; each toolhead including a prehem tool mounted thereon for movement relativethereto between: an inner use position for preforming prehemming of theperiphery of the outer member with respect to the periphery of the innermember, and an outer idle position spaced outwardly from the inner useposition; each tool head also including a final hem tool for completingthe hemming of the periphery of the outer member to the periphery of theinner member; a drive mechanism including a rotary actuator having anoutput that rotates 360 degrees, and said two vertical guides having theupper connections to the tool table also having lower connections to theoutput of the rotary actuator to move the tool table vertically on thebase from an upper start position downwardly through a hemming stroke toa lower position and then upwardly back to the upper start position inpreparation for another cycle; a first set of cam mechanisms for movingthe tool heads from outer idle positions on the tool table to inner usepositions during the initial downward movement of the tool table underthe impetus of the rotary actuator such that continued downward movementof the tool table then moves the prehem tool of each tool head toperform the prehem of the periphery of the outer member to the peripheryof the inner member; and a second set of cam mechanisms for moving theprehem tools of the tool heads from their inner use positions to theirouter idle positions upon farther downward movement of the tool table topermit the final hem tools to complete the hemming of the periphery ofthe outer member to the periphery of the inner member under the impetusof the rotary actuator as the tool table reaches the lower position. 18.A vehicle sheet metal hemming system comprising: a part supply forproviding vehicle sheet metal outer and inner members; a hemming machinefor cyclically hemming a periphery of an outer member to a periphery ofan associated inner member, and the hemming machine including a basehaving a stationary part mount that receives outer and inner members tobe hemmed to each other; robot apparatus including: a first robot forcyclically transferring outer members from the part supply to the partmount of the hemming machine, a second robot for cyclically transferringan inner member from the part supply to the part mount of the hemmingmachine after prior transfer of the associated outer member thereto, andthe second robot subsequently delivering the hemmed outer and innermembers from the hemming machine; the hemming machine including a tooltable having four tool heads mounted thereon for movement relative tothe table inwardly and outwardly with respect to the part mount on whichthe outer and inner members are mounted; four vertical guides thatsupport the tool table for vertical movement between an upper startposition and a lower position, the four tool heads being mounted betweenthe four vertical guides in an alternating relationship, two of thevertical guides having upper connections to the tool table, and theother two vertical guides having upper locators that cooperate with thesecond robot to locate the inner member during the hemming operation;each tool head including a prehem tool mounted thereon for movementrelative thereto between: an inner use position for preformingprehemming of the periphery of the outer member with respect to theperiphery of the inner member, and an outer idle position spacedoutwardly from the inner use position; each tool head also including afinal hem tool for completing the hemming of the periphery of the outermember to the periphery of the inner member; a drive mechanism includinga rotary actuator having an output that rotates 360 degrees, an electricmotor drive, a clutch and a gear reducer that drive the rotary output,the rotary output including a rotatively driven eccentric link and aconnection link having opposite ends one of which is connected to therotatively driven eccentric link, a connection bar having opposite endsand an intermediate portion connected to the other end of the connectionlink, and said two vertical guides having the upper connections to thetool table also having lower connections to the opposite ends of theconnection bar to move the tool table vertically on the base from anupper start position downwardly through a hemming stroke to a lowerposition and then upwardly back to the upper start position inpreparation for another cycle; a first set of cam mechanisms each ofwhich includes: four slotted cam members mounted on the base andrespectively associated with the four tool heads, and four roller camfollowers respectively mounted by the four tool heads and respectivelymoved by the four slotted cam members on the base to move the tool headsfrom outer idle positions on the tool table to inner use positionsduring the initial downward movement of the tool table under the impetusof the rotary actuator such that continued downward movement of the tooltable then moves the prehem tool of each tool head to perform the prehemof the periphery of the outer member to the periphery of the innermember; and a second set of cam mechanisms each of which includes: fourroller cams mounted on the stationary part mount of the base, and fourplate cam followers respectively mounted by the prehem tools of the fourtool heads and respectively moved by the four roller cams on stationarypart mount of the base to move the prehem tools relative to the toolheads from their inner use positions to their outer idle positions aftercontinued downward movement of the tool head subsequent to completingthe prehemming to permit the final hem tools to complete the hemming ofthe periphery of the outer member to the periphery of the inner memberunder the impetus of the rotary actuator as the tool table reaches thelower position.
 19. A method for hemming vehicle sheet metal comprising:operating robot apparatus to cyclically transfer a vehicle sheet metalouter member and an associated vehicle sheet metal inner member from apart supply to a hemming machine that includes a base having astationary part mount that receives outer and inner members to be hemmedto each other and that also includes a tool table supported for verticalmovement on the base and having a plurality of tool heads mountedthereon for movement relative to the table inwardly and outwardly withrespect to the part mount on which the outer and inner members aremounted; and operating a drive mechanism including a rotary actuatorhaving an output that rotates 360 degrees to move the tool tablevertically on the base from an upper start position downwardly through ahemming stroke to a lower position and then upwardly back to the upperstart position in preparation for another cycle, with a first set of cammechanisms moving tool heads on the tool table from outer idle positionsto inner use positions during the initial downward movement of the tooltable under the impetus of the rotary actuator such that continueddownward movement of the tool table then moves a prehem tool of eachtool head to perform a prehem of the periphery of the outer member tothe periphery of the inner member, and with a second set of cammechanisms subsequently moving the prehem tools of the tool heads frominner use positions to outer idle positions upon farther downwardmovement of the tool table to permit final hem tools of the tool headsto complete the hemming of the periphery of the outer member to theperiphery of the inner member under the impetus of the rotary actuatoras the tool table reaches the lower position.
 20. A method for hemmingvehicle sheet metal fuel door comprising: operating robot apparatus tocyclically transfer a vehicle sheet metal fuel door outer member and anassociated vehicle sheet metal fuel door inner member from a part supplyto a hemming machine that includes a base having a stationary part mountthat receives fuel door outer and inner members to be hemmed to eachother and that also includes a tool table supported for verticalmovement on the base and having a plurality of tool heads mountedthereon for movement relative to the table inwardly and outwardly withrespect to the part mount on which the outer and inner members aremounted; and operating a drive mechanism including a rotary actuatorhaving an output that rotates 360 degrees to move the tool tablevertically on the base from an upper start position downwardly through ahemming stroke to a lower position and then upwardly back to the upperstart position in preparation for another cycle, with a first set of cammechanisms moving tool heads on the tool table from outer idle positionsto inner use positions during the initial downward movement of the tooltable under the impetus of the rotary actuator such that continueddownward movement of the tool table then moves a prehem tool of eachtool head to perform a prehem of the periphery of the fuel door outermember to the periphery of the fuel door inner member, and with a secondset of cam mechanisms subsequently moving the prehem tools of the toolheads from inner use positions to outer idle positions upon fartherdownward movement of the tool table to permit final hem tools of thetool heads to complete the hemming of the periphery of the fuel doorouter member to the periphery of the fuel door inner member under theimpetus of the rotary actuator as the tool table reaches the lowerposition.